New Genetic Twist: 4-Stranded DNA Lurks in Human Cells

I'm Biv Dick Black, the Over Poster.

Sixty years after scientists described the chemical code of life — an interweaving double helix called DNA — researchers have found four-stranded DNA is also lurking in human cells.

The odd structures are called G-quadruplexes because they form in regions of deoxyribonucleic acid (DNA) that are full of guanine, one of the DNA molecule's four building blocks, with the others being adenine, cytosine, thymine. The structure comprises four guanines held together by a type of hydrogen bonding to form a sort of squarelike shape. (The DNA molecule is itself a double strand held together by these building blocks and wrapped together like a helix.)

The new visualization of the G-quadruplex is detailed this week in the journal Nature Chemistry.

"I think this paper is important in showing directly the existence of this structure in vivo in the human genome, but it is not completely unexpected," said Hans-Joachim Lipps, of the University of Witten in Germany, who was not involved in the study. [See Images of the 4-Stranded DNA]

Scientists had shown in the past that such quadruplex DNA could form in test tubes and had even been found in the cells of ciliated protozoa, or single-celled organisms with hairlike appendages. Also there were hints of its existence in human cells, though no direct proof, Lipps said.

But scientists still didn't have concrete evidence for its existence in the human genome. In the new study, researchers, including chemist Shankar Balasubramanian, of the University of Cambridge and Cambridge Research Institute, crafted antibody proteins specifically for this type of DNA. The proteins were marked with a fluorescent chemical, so when they hooked up to areas in the human genome packed with G-quadruplexes, they lit up.

Next, they incubated the antibodies with human cells in the lab, finding these structures tended to occur in genes of cells that were rapidly dividing, a telltale feature of cancer cells. They also found a spike in quadruplexes during the s-phase of the cell cycle, or the phase when DNA replicates just before the cell divides.

As such, the researchers think the four-stranded DNA could be a target for personalized medicine in the future. If they could block these odd ducks perhaps they could stop the rapid cell division of cancer cells.

"We are seeing links between trapping the quadruplexes with molecules and the ability to stop cells dividing, which is hugely exciting," Balasubramanian said in a statement.

The finding "is certainly a technical (not scientific) breakthrough in designing antibodies sensitive enough to demonstrate this structure in vivo in the human genome," Lipps wrote.

Lipps and his colleagues had suggested previously these structures regulate basic biological mechanisms, such as the replication of DNA.

"What makes me personally very happy about this work is that it again demonstrates that mechanisms first described in ciliated protozoa hold also true for other organisms up to human, demonstrating the strength of this model organism," wrote Lipps wrote.

The team still has several questions about quadruplexes, such as how the structures operate. "One thought is that these quadruplex structures might be a bit of a nuisance during DNA replication — like knots or tangles that form," Balasubramanian said.

Not really. I think most cancer hits people after reproductive age, so that's not a major issue. People just live longer. Yes, that creates population pressure, but not nearly as much as something that would save lives in reproductive age people, like stopping drinking and dumbass shit that young people do.

People will still die of old age.

OTOH, the really tricky thing about cancer is that to "cure" it, we need to really understand it. If we understand it, then we also have the key to true long age. Some (all?) cancer cells are immortal. For at least some of them, the telomeres that shorten with each cell division and therefore cause senescence in cells (why we get old) simply don't shorten. Now THAT will cause a population problem, eventually. But it'll happen slowly enough that we have a decent chance of getting ahold of it, societally.

"Curing" cancers kind of a tricky thing, though. I mean, we know what cancer is. We know what causes it, at a certain level. Cancer is just a transcription error when your cells divide that the body's proofreaders miss and destroys you. Viruses can cause cancer, chemicals can cause cancer, sunlight can cause cancer, and just pure random chance when your body's trillions of cells reproduce millions of genes dozens of times a year. A computer copying files can fuck up if there's something wrong with the hard drive, wrong with the copying medium, the computer gets bumped while copying the files, there's a surge in the power line, you bring a powerful magnet close by, and just pure random chance as millions of bits are copied. Same concept. We might be able to eliminate the outside agencies that cause cancer, like viruses, chemicals, sunlight, radiation, etc. But random chance will still cause it. Until we truly develop reliable nanobots to sweep our bodies for cancer cells (which isn't really a "cure", per se), cancer will be with us.